The Greatest Generation is tired. In their day, with hearts clanging in their skinny, young chests, they flew bomb runs, manned the machine guns on 7,000 cargo ships or survived 124 days in a foxhole on an Italian beach surrounded on three sides by German troops.

Now, it takes all that a citizen soldier such as Eugene Lafferty has to climb the stairs at the National Air and Space Museum's Steven F. Udvar-Hazy Center. One by one, the 81-year-old widower labors up the steps with his cane. "I'm about out of steam," he said this weekend at his unit's reunion. They are old, their faces marked with wrinkles and age spots, and the once-easy gait of young men who didn't know any better has become the stiff, cautious step of old men who have seen too much.

Lafferty climbs the stairs and joins other men who served with him in the U.S. Navy Armed Guard. They come together at reunions such as this, the ones who are left and those who can, because they must. You had to have been there to understand.

During World War II, there were 16.4 million of them, men and women in uniform, ready, as the saying goes, to do nothing less than save the world. Now, 3.5 million are left.

The Department of Veterans Affairs estimates that 1,000 die every day. And some, such as C.A. Lloyd, are beginning to realize they aren't going to go on forever.

For 25 years, Lloyd, of Rolesville, N.C., has organized the annual reunion of the veterans of the Navy Armed Guard, the guys who guarded the ships that carried 373 million tons of cargo to and from U.S. ports during the war. But this year's reunion, he said, is going to be their last.

"It's age," he said. "It's catching up on us. I'm 80, and I'm the youngest one here."

Their counterparts in England have held their last reunion. The ones in Australia, too. "They're all closing up," he said.

Ten years ago, 1,100 veterans went to their reunion in Las Vegas to find their war buddies and relive old times. This weekend, in and around Washington, there are fewer than 200. And instead of a full day of sightseeing as in the old days, the bus trip to the Udvar-Hazy Center was the only thing on the agenda Friday.

Yesterday, on their trip to the U.S. Navy Memorial, where they laid a wreath and searched computers there for their stories, and to the World War II Memorial, Lloyd made sure that the five buses would pull up as close as possible to make it easier for those with walkers, canes and wheelchairs.

Why do they go, year after year, to nondescript hotel convention centers and don matching baseball caps and windbreakers and pin on oversize nametags? Go up to the Navy Armed Guard's hospitality suite, above the sweating bodies in the gym at the Hilton Washington Dulles Airport Hotel, and listen.